The biostatisticians' objectives are to assure that sound methods of study design and analysis are used to meet the specific aims of this program project, to develop procedures for applying recent advances in biostatistical methodology, and to develop new statistical and mathematical methods where needed. The biostatistical group will also take the lead in a systematic study of prognostic factors for each of the major clinical endpoints experienced by marrow transplant recipients using the substantial database accumulated over the past 15 years. The increased size of the marrow transplant program creates large quantities of data. In this situation it is increasingly difficult for investigators to examine and manipulate data generated in all parts of the system. Maintaining such a flow of information is a central objective of this core component. A new cental storage facility has been installed, adequate terminal access will be provided and lucid and effective software will be developed to encourage frequent and direct retrieval by the project investigators. The efficiency of data input will be improved by direct data entry from the source, by transferring types of data entry from core input to distributed input and by automating the system as much as possible.